Abstract

Over the last 5 years (2012-17), an increasing area of grass pastures, both sown and native, have been dying in patches across multiple districts in eastern Queensland. Symptoms are the same or similar to buffel grass dieback that was first observed in the early 1990’s, that is yellowing and reddening of leaves, stunting and eventual death. Once the pasture has died, the area is typically colonised by a range of broadleaf plants, including weeds, small shrubs, legumes or other (generally undesirable) grasses. Graziers with pastures impacted by this condition have grave concerns about the progressive destruction of pastures, and are looking for answers to ensure the long-term profitability of businesses.The term ‘dieback’ has been used to describe a range of conditions with unrelated causal agents across a broad range of plant types, including trees, shrubs, legumes and grass pastures. While an array of literature has been published about dieback in plant communities, there are relatively few publications specifically outlining dieback in pasture systems utilised by grazing animals (beef and dairy cattle, sheep). A range of pathogens have been identified as causes of dieback in other plants, including fungal root and leaf diseases, and a range of these have been isolated from plant samples affected by pasture dieback in central Queensland. Recent plant testing, and past research including a PhD study, have been unable to determine the causal agent or define the contributing factor(s) of dieback in central Queensland pastures. It is possible that the condition is a complex interaction of multiple contributing factors, for example plant pathogens, insects, soil fertility and moisture stress.Approximately 120 landholders have reported pasture dieback on their properties, and about 35,000ha of pastures are known to be affected, spanning from south-east Queensland, Burnett, central Queensland, Mackay/Whitsunday and North Queensland (as of July 2017). While the entire 35,000ha is not completely affected as generally patches of pasture are affected across this area, the actual area affected is likely to be significantly higher than this due to not all reports being captured by Department of Agriculture and Fisheries staff and other industry organisations. Also, many graziers are unfamiliar with the disease and therefore don’t realise they have pasture dieback, and anecdotal reports indicate some graziers are reluctant to tell authorities they have the disease due to biosecurity concerns, or the potential of land de-valuation by banks.The development and funding of a research project to investigate pasture dieback is a high priority, due to the rapidly expanding area of affected pastures across Queensland being reported and the uncertainty of the cause. There has been relatively little research on pasture dieback in the past compared to the value of the sown grasses being affected. Past research relied on modest budgets, focussed on only a few sites and did not investigate all the possible causal agents. Future research needs to build on past studies where possible, however a coordinated, systematic approach using a multi-disciplinary team is required to provide a better chance of determining what the causal agent(s) are and what the best management practices are likely to be. In total, five priorities for future research, development and extension have been identified. These include: 1. Understanding the extent of the condition, now and into the future; 2. Determining specific details of outbreaks and commonalities across sites; 3 Determining causal factor(s); 4. Determining management solutions; 5. Engaging with industry. Currently, such as proposal that addresses these priorities is under consideration by Meat and Livestock Australia (MLA).